The objective of this proposal is to exploit the unique advantages offered by gene fusions to study various aspects of ribosomal RNA genetics and control. The fusion of two different operons has provided an added dimension to the selective techniques available to the molecular geneticist and has provided a facile means of observing the regulation of genes specifying products which are not readily measured. Restriction endonucleases and recombinant DNA technology make possible the assembly of genetic information from a variety of sources in a highly controlled fashion. We have constructed gene fusions between ribosomal RNA operon control regions and part of the well-characterized lactose operon. With these fusions we propose to: (a)) study the influence of various treatments on a single ribosomal control region, (b) use fusions to the seven different ribosomal cistrons to compare their individual expression, (c) apply selective pressure for isolation of mutants either in the rrn control region or in other genes which interact with it and (d) study and manipulate the control region in vitro. It will further allow us to investigate the mechanism of any molecular interactions with the ribosomal control region. DNA sequencing is used to plan fusion schemes, to identify the cloned fusion sequence and to determine precise differences between wild type and mutant ribosomal control region alleles.